Obstetrical instrument for rupturing the amniotic sac

ABSTRACT

AN OBSTERTRICAL INSTRUMENT FORMED INTEGRAL WITH A FINGER OF A SURGICAL GLOVE INCLUDING A FLEXIBLE SHEATH ALONG THE BACK SURFACE OF A FINGER OF THE GLOVE, A MOVABLE FLEXIBLE BLADE ENCLOSED IN THE SHEATH AND EXTENDABLE BY A BUTTON PROJECTING THROUGH A SLOT ALONG THE TOP FACE OF THE SHEATH ENGAGEABLE BY THE PALM SIDE OF AN ADJACENT FINGER, THE BLADE HAVING AN EXPOSED POINT WHEN EXTENDED FOR RUPTURING THE AMNIOTIC MEMBRANE OF A PREGNANT WOMAN TO RELEASE THE AMNIOTIC FLUID PREPARATORY TO DELIVERY OF THE BABY.

United States Patent 1 1 3,587,591

[72] 1nven10r Raymond D. Salterwhite 2,668,536 2/1954 Farries et a1.128/305 5182 Ollie, Fort Worth, Tex. 76119 2,811,969 11/1957 Shubert128/303 [2]] Appl. No. 774,888 2,847,012 8/1958 Eastman.. 128/303 [22]Filed Nov. 12,1968 3,126,890 3/1964 Deming 128/361 [45] Patented June28,197] 3,362,408 1/1968 Stocki et a1.. 128/314 3,410,269 11/1968 Hovick128/361 54 OBSTETRICAL INSTUMENT r011 RUPTURING Dalton TruluCk THEAMMOTIC SAC AtI0meyH. Mathews Garland 13 Claims, 9 Drawing Figs.

110/2981 128/329 ABSTRACT: An obstetrical instrument formed integralwith a [51] Int. Cl A611) 17/42 finger of a Surgical glove including aflexible Sheath along the [50] Fleld 01' Search 128/303, back Surfaceofa finger of the glove, a movable flexible blade 305, 307, 314, 315,329, 361; 30/298; enclosed in the sheath and extendable by a buttonprojecting 2/(Inqu" ed) through a slot along the top face of the sheathengageable by the palm side of an adjacent finger, the blade having anex- [56] References (med posed point when extended for rupturing theamniotic mem- UNITED STATES PATENTS brane of a pregnant woman to releasethe amniotic fluid 1,512,943 10/1924 Martineau 30/298X preparatory todelivery of the baby.

I'II'II I PATENIEU JUN28 I971 SHEET 1 UF 2 Fig.4

Fig.|

INVENTOR. Raymond D SoHerwhHe m ue ATTORNEY OBSTETRICAL INSTUMENT FORRUPTURING THE AMNIOTIC SAC This invention relates to obstetricalinstruments and more particularly to an obstetrical instrument forrupturing the amniotic membrane at the internal opening of the cervix torelease the amniotic fluid surrounding a baby in the uterus of a womanpreparatory to delivery of the baby.

The amniotic membrane or sac encloses the embryo and the fetus, as theinfant is known after the second month, which is cushioned in a fluidenvironment provided by the amniotic fluid contained within the sac. Asthe fetus grows and the sac enlarges the quantity of amniotic fluidincreases to provide cushioning or protection for the enlarging infant.The amount of the amniotic fluid surrounding the baby may be sufficientthat when labor begins the muscles contracting to expel the baby fromthe uterus are ineffective because of the volume of amniotic fluid whichis absorbing the energy and precluding expulsion of the baby. The babymay be merely moved around within the uterus thereby delaying the birth.Amniotomy or rupture of the amniotic membrane is a well known old andeffective way of inducing labor, or if labor has started, it may rendermore effective the muscular contractions of labor when they are advancedenough to produce delivery. Under any circumstances it is generallypreferred that the rupture be followed by delivery of the baby within areasonable period of time, such as within about 24 hours, in order tominimize the hazard of infection to the mother and baby. When themembrane is so ruptured labor often may follow with subsequent birthwithin 1 or 2 hours.

One method of rupturing the amniotic membrane commonly used has includedthe use of the Allis clamp which is not specifically designed for thistechnique or type of operation and which not only requires the insertionof two fingers of one hand of the operating physician into the vaginaand cervical canal but additionally requires the insertion of the Allisclamp which must be manipulated by the other or external hand of thephysician. The Allis clamp method thus requires both hands of thephysician and substantial dilation of the cervical opening. Othermethods of performing the operation include using an extensible cuttersupported along the palm side of one finger of the physician andoperable by a flexible rod extending to an indicator member positionedalong the wrist of the physician with the rod being bent by flexing thewrist and the indicator showing the position of the cutter element. Theinstrument is fairly easily displaced on the physician's fingers andalso requires the extension of a portion of the instrument outwardly ofthe cervical canal and the vagina. A still further approach to rupturingof the sac has included a finger piece or portion of a surgical glovehaving an exposed puncturing point formed thereon and requiring that thesupporting finger be held against one side of the vagina and cervicalcanal away from the exposed point to prevent tearing of the tissueduring the insertion and positioning of the finger to properly rupturethe sac. Thus, in general the prior art has either included mechanismrequiring undue protection against tearing of the tissue, the use of twohands, or structure which somewhat limits the ability of the examiningand rupturing finger to freely move within the area of the portion ofthe sac to be punctured.

It is, therefore, an object of the invention to provide an obstetricalinstrument particularly adapted to the rupture of the amniotic sac ormembrane for release of amniotic fluid from the uterus preliminary todelivery ofa baby.

It is another object ofthe invention to provide an obstetricalinstrument of the character described which is insertable through thevagina and connecting cervical canal to the opening of the cervicalcanal into the uterus where the instrument is activated to rupturetheportion of the amniotic sac covering the opening of the cervical canalinto the uterus.

It is a further object of the invention to provide an obstetricalinstrument of the character described which is accommodated to thefinger of the operating physician by formation of the instrumentintegral with a surgical glove finger such that substantial flexibilityof the operating finger is maintained to permit manipulation of thefinger to the rupturing the membrane. v

It is a particularly important object of the invention to provide anobstetrical instrument of the character described which has smoothcontoured surfaces permitting insertion along the'vaginal and cervicalcanals to the point of membrane rupture without tearing or unnecessarilyirritating the tissue defining each canal thus providing maximumprotection to such tissue without holding the operating finger in anyspecial position or along any one surface of either canal duringinsertron.

It is another object of the invention to provide an obstetricalinstrument of the character described including an extendable cuttingpoint held at a retracted protected position until the operating fingeris at a rupturing position along the membrane and is then extended to arupturing position.

lt is still a further object of the invention to provide an obstetricalinstrument of the character described which includes a blade movablefrom a protected retracted position to extended rupturing position by anadjacent finger of the operating physician when the operating finger iswithin the cervical canal.

It is another object of the invention to provide an obstetricalinstrument of the character described having a cutting blade pointaligned at an angle which permits withdrawal of the operating fingerwithout engaging and tearing tissue defining the cervical and vaginalcanals.

It is a further object of the invention to provide an obstetricalinstrument of the character described having a cutting blade extendableand lockable at operating position by a single movement of an adjacentfinger of the physician. v

It is another object of the invention to provide an obstetricalinstrument of the character described which may be economicallyconstructed of sterilizable materials so that the surgical gloveincluding the integral instrument is expendable and thus may be used foronly a single operation and discarded.

it is a still further object of the invention to provide an obstetricalinstrument as described including a flexible sheath formed along theback side of one finger of a surgical glove, and a knife enclosed withinthe sheath and movable from a retracted to an extended position at whicha membrane piercing point on the knife projects through an opening inthe sheath disposed along the tip end of the finger of the glove.

It is another object of the invention to provide an obstetricalinstrument of the character described in which the finger of thesurgical glove carrying the instrument is reinforced while retaining itsflexible character and is sufficiently thin that the sensitivity of theoperating finger of the physician within the glove finger is essentiallyretained.

It is still a further object of the invention to provide an obstetricalinstrument of the character described having a membrane rupturing pointof limited length so that the amniotic sac may be ruptured whileminimizing possibility of damage to the baby.

It is another object of the invention to provide an obstetricalinstrument as described wherein the knife blade is locked againstretraction once moved to its extended position.

Additional objects and advantages of the invention will be readilyapparent from reading the following description of the deviceconstructed in accordance with the invention and by reference to theaccompanying drawings thereof wherein:

FIG. 1 is a view in perspective of a surgical glove including anobstetrical instrument constructed in accordance with the inventionsecured along one finger of the glove;

FIG. 2 is an enlarged fragmentary top view of the instrument and aportion of its supporting surgical glove finger with the blade at itsretracted position;

FIG. 3 is a side view in section along the line 3-3 of FIG. 2;

FIG. 4 is a transverse view in section along the line 4-4 of FIG. 3;

FIG. 5 is a view in section a similar to FIG. 3 with the blade properposition for extended to expose the point at membrane-rupturingposition;

FIG. 7 is an enlarged fragmentary top plan view of a portion of theblade of FIG. 6 showing the membrane rupturing points of the blade;

FIG. 8 is a sectional view of the female human anatomy carrying a childduring pregnancy with the operating finger of the physician carrying theobstetrical instrument inserted into the cervical canal; and

FIG. 9 is a view in section similar to FIG. 8 with the membrane-piercingpoint of the instrument blade extended and piercing the membranecovering the opening of the cervix into the uterus. Referring to thedrawings, an obstetrical instrument embodying the invention is disposedalong the back or top and end surface of a finger 21 of a surgical glove22 formed of a thin latex rubber or plastic film which may be of athrowaway or disposable type. Such gloves are well known and serve tominimize infection danger by fully covering the hand of the operatingphysician while preserving the sensitivity of the fingers to touch. Theinstrument is preferably formed integral with the glove finger ofamaterial compatible with the material forming the glove.

The instrument 20 includes a sheath or housing 23 contouredsubstantially to the shape of the glove finger 21 when fitted on thefinger 24 of an operating physician as illustrated in FIG. 3 so that inuse it will conform as closely as possible to the shape of thephysician's operating finger 24. The sheath 23 is disposed along theback surface 25 and an upper portion of the tip surface of the glovefinger. The sheath is provided with an internal longitudinal recess 31extending along the back face of the glove finger 21 and openingdownwardly and outwardly through a slot 32 across the tip end of theglove finger. A locking cleat 33 is formed with the sheath projectingdownwardly into the recess 31 as seen in FIG. 3. The front face 33a ofthe locking cleat is formed at an acute angle with the top surface ofthe recess 31. A substantially rectangular slot 34 extends along the topof the sheath opening into the recess 31. The back end portion 23a ofthe sheath 23 is thickened behind the recess 31 and gradually decreasesin thickness and is arcuate in shape as viewed in plan in FIG. 2 so thatits top surface blends into the back face of the glove finger 21 toprovide a smooth continuous surface connection between the sheath andthe glove finger surfaces so that the glove finger with the obstetricalinstrument will slide smoothly without tissue damage or irritationthrough the vaginal and cervical canals during insertion to operatingposition. Laterally, as viewed in FIG. 4, the sheath 23 is graduallyreduced in thickness as it extends downwardly and integrally joins askirt or envelope 35 of relatively thin material fully encasing theglove finger along its side, palm and tip surfaces as evident in FIGS.3-and 4. The envelope 35 is formed as thin as practicable to reinforcethe portion of the glove finger 21 supporting the sheath 23 whileincreasing the total thickness of the combined glove finger and envelopea minimum-to retain the sensitivity of the sense of feel of thephysician's finger within the glove finger. Also, it is preferred thatmaximum mobility or flexibility ofv the physician's finger be retainedconsistent with structural strength of the glove along the fingerportion 21 supporting the instrument 20.

A blade 40 having a membrane puncturing tip portion 41 bifurcated toprovide dual points 42 is slidably disposed in the recess 31 of thesheath 23. The blade is slightly narrower tan the width of the recess31, FIG. 4, and slightly shorter than the length of the recess, FIG. 3,so that at its fully retracted position it is fully encased within therecess. The relatively small tolerance between the width of the bladeand the width of the recess insures substantially straight movement ofthe blade from its retracted to its extended position and holds theblade substantially rigid laterally at its extended operating position.An operating handle and lock 43 is secured on the top face of the bladefor engagement by a finger of the operating physician to move the bladefrom its retracted position of FIG. 3 to its extended position of FIG. 5and to lock the blade at such extended position. The handle 43 isnotched at 44 providing the blade makes an acute angle with the top face51' of the blade corresponding substantially to the angle of the face.33 on the locking cleat 32 for locking the blade at its extendedposition. The top face of the handle 43 is serrated or roughed as at 46to facilitate engagement by the physician's finger for moving the bladefrom its retracted to its extended position.

Between the dual tips 42 the blade is provided with an arcuate concaveend recess 42a of a depth as measured from a line between the dual tipssubstantially the thickness of the average amniotic membrane to providea safety factor rending to limit the penetration of the tip into themembrane to minimize possibilities of damage to the baby. The blade isinherently bent as to the curvature shown in FIG. 6 such that a majorportion of its bottom face 400 is convex while its top face 40b isgenerally concave when relaxed. When the blade is extended it is thendistorted to the shape shown in FIG. 5 so that it binds somewhat as itpasses through the slot 32 holding it more tightly in place at itsrupturing position. A further element of control of the depth to whichthe points may penetrate a membrane is provided by the extent ofprojection of the rupturing tips beyond the end or tip of the envelope35 as seen in FIG. 5. The curvature of the end portion of the bladealong with the angle ofthe opening of the slot 32 and the overhang ofthe thickened top end portion of the sheath 23 above the slot 32relative to the tip portion of the envelope 35 combine to control theextent to which the blade tips are generally inserted into or penetratethe membrane along with, of course, the technique of the operatingphysician.

The sheath 23 and the envelope 35 are formed of latex rubber or plasticmaterial having sufficient rigidity to properly house and hold the blade40 while being as flexible as possible to provide maximum mobility tothe operating finger 24 of the physician inserted into the glove finger21 when the instrument is in use. Also, the material forming the sheathand envelope must be readily securable to the surgical glove finger sothat the glove finger, instrument sheath, and envelope functionessentially as one during operation ofthe instrument.

The blade 40 and the handle 43 also may be formed of a plastic which,however, must have sufficient rigidity to permit it be sharpened at thepoints 42 to the extent required for readily rupturing the amnioticmembrane.

The operation of the obstetrical instrument 20 is illustrated in FIGS. 8and 9 showing a section of a pregnant woman in a reclining position atwhich delivery is normally accomplished. When the physician hasdetermined that the patient has arrived at the proper stage theinstrument may be used to rupture the amniotic membrane 55 along themembrane portion 55a over the opening 56 from the cervix 57 to theuterus 58. The physician's hand covered by the surgical glove with theobstetrical instrument is inserted into the vagina 60 of the patientwith the palm side of the hand facing the top 6011 of the vagina orforward with respect to the patient and the back side of the handextending along the bottom 60b of the vagina. The finger carrying theinstrument is advanced along the vagina to the cervical canal with thedistal portion of the finger being bent somewhat for entry into thecervical canal and further penetration to the entrance 56 of the canalinto the uterus. A particularly important feature of the instrument isthat during the insertion through the vagina and the cervical canal thesmooth contours of the surfaces of the instrument and the retractedposition of the blade minimize any tearing or irritation of thesurrounding tissue and does not require special positioning of thefinger to avoid tissue damage. As the physicians finger moves along thevagina it reaches the external opening 61 of the cervical canal 62 wherethe finger is advanced upwardly through the canal toward the uterus. Asthe operating finger advances in the cervix the hand and the fingerpositioned with the palm side of the finger upwardly in the cervix sothat when the opening 56 of the cervix into the uterus is reached thethinner portion of the envelope 35 of the instrument spaced toward thepalm side of the finger 21 from the knife opening 32 reaches themembrane portion 55a so that the physician can feel the membrane withthe tip .of his finger 24. The operating finger may be used to carefullypartially strip back the amniotic membrane from the uterine attachmentand allow an accumulation 62a of the amniotic fluid 62 along the top ofthe head of the baby along the portion 55a of the membrane. Thisprovides more fluid protection and further spaces the membrane from thehead of the baby during the rupture step.

When the physician has determined that he has made the proper contactwith the membrane 55 and has prepared the membrane by fingermanipulation for rupturing to the extent desired, the blade 40 isextended for the membrane rupturing step. The operating finger is in theposition in the cervix at the membrane as shown-in FIG. 8. The indexfinger 24a of the physician is moved laterally into overlappingrelationship with the operating finger with the palm side of the distalportion of the index finger engaging the surface 46 of the handle 43.The index finger is straightened toward the end of the operating fingeradvancing the blade 40 in its recess 31 toward the tip of the operatingfinger extending the top portion of the blade through the opening 32 inthe sheath 23 to the fully exposed position of H68. 5 and 9. As theblade is extended through the slot it is bent downwardly as viewed inFIG. 5. When the back edge face 50 of the blade passes the locking cleat32 the bending stress in the blade causes the back end portion of theblade to spring upwardly into the notch defined at the front face 33a ofthe cleat 33. The angle of the back edge 50 of the blade and the frontface 33a of the cleat correspond so that the face 50 seats against thecleat face 33a to lock the blade against retraction. Also, the upwardspringing of the blade moves the handle 43 to the position of FIG. 5 atwhich the flange portion 45 overlaps the top surface of the sheath 23toward the free end of the instrument locking the blade against theflexing inwardly so that the blade cannot be moved to disengage its backface 50 from the locking cleat face 33a. The tips 42 project outwardlyfrom the opening 32 in the sheath and divurgently with respect to theend surface of the envelope 35. The operating finger 24 is then gentlybent toward its palm side, upwardly in terms of FIG. 9, and drawn alongthe membrane portion 55a causing rupturing of the membrane covering theopening of the cervix into the uterus. The extent of movement requiredby the operating finger, the exact angle of the blade tip with themembrane, and other factors involved in effecting the membrane rupturewill, of course, vary with patients and are within the control andjudgement of the physician. When he has determined that the membrane isproperly ruptured by the draining of the amniotic fluid from the uterusthrough the cervix and the vaginal canal, the obstetrical instrument isremoved by gently withdrawing the hand of the physician until it hasbeen completely removed from the patient. Since the rupturing blade islocked at its extended position, some care must be exercised during thewithdrawal step not to damage the tissues around the cervical andvaginal canals. As evident from the view of FIG. 9 this may be carriedout by gently pressing the operating finger towards it back side or inother words, downwardly along the bottom or back surface 57a of thecervical canal and 60b of the vaginal canal. Such movement of theoperating finger will maintain it spaced from the opposite or top sidesof the cervix and vagina and the sloping or convergence of the endportion of the blade toward the palm side of the distal portion of theoperating finger insures against contact of the tips 42 with the tissueof the cervix and vagina. After the physicians hand is removed and themembrane is known to be properly ruptured, the surgical glove with theinstrument may be removed and disposed of.

It will be evident from the description of the operation of theinstrument that it is preferred that the envelope 35 be as thin aspracticable consistent with proper securing of the instrument on thesurgical glove finger so that maximum sensitivity of the palm surface ofthe physicians finger may be retained and also that the envelope andfinger portion of the glove be as tight as practicable on the finger ofthe physician to enhance its sensitivity to aid in his'ability todetermined the proper location and conditions for rupture of themembrane.

The instrument 20 has been illustrated and described on the secondfinger next to the index finger though it is to be understood that theinstrument may be formed on any desired finger of a surgical glove foruse on either hand ofa physician. The exact shape of the blade tips 42,their spacing. and the depth of the end recess 42a are varied asrequired. The blade also may be made with a single piercing point. Also,the angle of divergence of the extended blade end portion 41 with theadjacent surface of the end of the envelope 35 may be varied to satisfydifferent membrane thickness and membrane cervical canal angleconditions. Where the material forming the blade 40 is sufficientlystiff the blade may remain at its extended locked position as in FIG. 5without the need for the locking flange 45 on the handle 43 and thusunder such conditions the flange may be dispensed with. Care must beexercised in forming the ribbed surface 46 that it is easily engaged bya finger to extend the blade but is not so rough that tissue will beirritated or torn by contact with it.

It will now be seen that a new and improved obstetrical tool for ruptureof the amniotic membrane in a pregnant woman preliminary to delivery ofher child has been described and illustrated. It will be seen that theinstrument includes an extendable blade which is enclosed as a fullyretracted position during insertion of the physicians operating fingerand hand to membrane rupturing position thereby minimizing tissue damagealong the surfaces of both the vagina and the cervix. it will be furtherseen that the instrument is tightly secured on the operating finger ofthe surgeon maintaining the sensitivity of the finger through the palmside of the surgical glove finger supporting the instrument. It willalso be recognized that the integral instrument glove unit may beeconomically manufactured and subsequently disposed of after use.

The foregoing description of the invention is explanatory. only andchanges in the details of the construction illustrated may be made bythose skilled in the art within the scope of the appended claims withoutdeparting from the spirit of the invention.

What is claimed and desired to be secured by Letters Patent is:

lclaim: 1

1. An obstetrical instrument for rupturing an amniotic membrane forrelease of amniotic fluid within the membrane to facilitate the birth ofa baby contained therein, said instrument comprising: a sheath adaptedto be secured along the back of a finger; a blade supported in saidsheath for axial movement between a retracted fully incased positionwithin said sheath and an extended locked position at which a free endportion of said blade projects from said sheath along an end of saidfinger for rupturing said amniotic membrane by manipulation of saidfinger, an operator member connected with said blade and engageable byan adjacent finger on the hand of an operator supporting said instrumentfor moving said blade from said retracted to said extended positionresponsive to movement of said adjacent finger only; said blade and saidsheath being operatively interrelated whereby said blade resistsextension from said retracted position and is positionable in saidextended position by said adjacent finger only and locking means withinsaid sheath and on said blade operator member cooperating together tolock said blade at said extended position, said operator memberincluding a locking flange coacting with a surface of said sheath forlocking said blade.

2. An obstetrical instrument as defined in claim 1 wherein said sheathis secured along a finger piece adapted to fit said finger.

3. An obstetrical instrument as defined in claim 2 wherein said fingerpiece is one finger ofa surgical glove.

4. An obstetrical instrument as defined in claim 3 including areinforcing envelope connected with said sheath over said finger of saidglove for holding said instrument along said glove finger..

5. An obstetrical instrument as defined in claim 4 wherein said sheathand said envelope are fused with said glove finger whereby said sheathand said envelope are substantially integral with said glove finger.

6. An obstetrical instrument as defined in claim wherein said sheath,said envelope, and said blade comprise flexible material permittingmobility of said finger within the surgical glove finger in saidenvelope and sheath.

7. An obstetrical instrument as defined in claim 6 wherein said operatormember comprises a handle on said blade projecting through said sheathfor moving said blade from the retracted to the extended position.

8. An obstetrical instrument for rupturing an amniotic membrane forrelease ofamniotic fluid within the membrane to facilitate birth of ababy contained therein, said instrument comprising: a sheath havingcontoured internal and external surfaces adapted to conformsubstantially to the shape of the top, upper side, and end surfaceportions of a finger'supporting said instrument, said sheath extendingsubstantially from the second joint of said finger along the top surfacethereof around upper free end surface portions of said finger; areinforcing envelope secured with said sheath and adapted to conform tothe side, bottom, and end portions of said finger, said envelopeconnecting with said sheath along upper side and end edges; said sheathand said envelope being secured on a finger of a surgical glove withsaid sheath extending along the back and upper end surface portions ofsaid glove finger; said sheath being provided with an internal recessclosed at an end near said second joint of said finger extendinglongitudinally along the back surface of said supporting glove fingerand opening at the free end of said glove finger through a transverseslot provided in said sheath at said end of said glove finger; saidsheath having a longitudinally extending slot communicating through theupper surface thereof into said recess within said sheath; a lockingcleat formed within said sheath projecting into said recess in saidsheath between said closed end and said slot opening through the topsurface of said sheath into said recess; a blade longitudinally disposedwithin saidrecess of said sheath for movement between a retractedposition at which said blade is fully encased within said sheath and anextended position at which an end portion of said blade projects fromsaid recess of said sheath through said slot at the free end of saidsheath; means providing a point on said blade at the end portion of saidblade extendable from said sheath for engaging and rupturing saidamniotic membrane when said blade is at said extended position; anoperating handle on said blade projecting through said slot in the topof said sheath for moving said blade from its fully encased retractedposition to said extended position, the distance said handle is movablein said slot of said sheath determining the length of the stroke of saidblade between said retracted and said extended positions; and said bladebeing shaped to direct the pointed end portion of said blade throughsaid slot along the free end of said glove finger and flexing the inwardend of said blade upwardly toward said locking cleat whereby when saidblade is fully extended the inward end of said blade engages said cleatfor locking said blade at said extended position. v

9. An obstetrical instrument as defined in claim 8 wherein saidprojecting end portion of said blade when extended is disposed at anacute angle with the end surface portion of said envelope disposed overthe end of said glove finger whereby movement of said glove finger inthe direction of the palm side of a finger therein engages said point onsaid blade with said amniotic membrane.

10. An obstetrical instrument as defined in claim 8 wherein said bladeis provided with a bifurcated end having dual membrane puncturing pointsspaced on opposite sides of an arcuate recess having a depthsubstantially defining the extent of penetration of said points into amembrane punctured by said blade points.

11. An obstetrical instrument as defined in claim 8 including a lockingflange on said handle for engaging said sheath along said slot in thetop of said sheath for locking said blade at said extended osition.

12. An obstetrical instrument as defined in clalm 8 wherein

